1menu "printk and dmesg options" 2 3config PRINTK_TIME 4 bool "Show timing information on printks" 5 depends on PRINTK 6 help 7 Selecting this option causes time stamps of the printk() 8 messages to be added to the output of the syslog() system 9 call and at the console. 10 11 The timestamp is always recorded internally, and exported 12 to /dev/kmsg. This flag just specifies if the timestamp should 13 be included, not that the timestamp is recorded. 14 15 The behavior is also controlled by the kernel command line 16 parameter printk.time=1. See Documentation/kernel-parameters.txt 17 18config MESSAGE_LOGLEVEL_DEFAULT 19 int "Default message log level (1-7)" 20 range 1 7 21 default "4" 22 help 23 Default log level for printk statements with no specified priority. 24 25 This was hard-coded to KERN_WARNING since at least 2.6.10 but folks 26 that are auditing their logs closely may want to set it to a lower 27 priority. 28 29config BOOT_PRINTK_DELAY 30 bool "Delay each boot printk message by N milliseconds" 31 depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY 32 help 33 This build option allows you to read kernel boot messages 34 by inserting a short delay after each one. The delay is 35 specified in milliseconds on the kernel command line, 36 using "boot_delay=N". 37 38 It is likely that you would also need to use "lpj=M" to preset 39 the "loops per jiffie" value. 40 See a previous boot log for the "lpj" value to use for your 41 system, and then set "lpj=M" before setting "boot_delay=N". 42 NOTE: Using this option may adversely affect SMP systems. 43 I.e., processors other than the first one may not boot up. 44 BOOT_PRINTK_DELAY also may cause LOCKUP_DETECTOR to detect 45 what it believes to be lockup conditions. 46 47config DYNAMIC_DEBUG 48 bool "Enable dynamic printk() support" 49 default n 50 depends on PRINTK 51 depends on DEBUG_FS 52 help 53 54 Compiles debug level messages into the kernel, which would not 55 otherwise be available at runtime. These messages can then be 56 enabled/disabled based on various levels of scope - per source file, 57 function, module, format string, and line number. This mechanism 58 implicitly compiles in all pr_debug() and dev_dbg() calls, which 59 enlarges the kernel text size by about 2%. 60 61 If a source file is compiled with DEBUG flag set, any 62 pr_debug() calls in it are enabled by default, but can be 63 disabled at runtime as below. Note that DEBUG flag is 64 turned on by many CONFIG_*DEBUG* options. 65 66 Usage: 67 68 Dynamic debugging is controlled via the 'dynamic_debug/control' file, 69 which is contained in the 'debugfs' filesystem. Thus, the debugfs 70 filesystem must first be mounted before making use of this feature. 71 We refer the control file as: <debugfs>/dynamic_debug/control. This 72 file contains a list of the debug statements that can be enabled. The 73 format for each line of the file is: 74 75 filename:lineno [module]function flags format 76 77 filename : source file of the debug statement 78 lineno : line number of the debug statement 79 module : module that contains the debug statement 80 function : function that contains the debug statement 81 flags : '=p' means the line is turned 'on' for printing 82 format : the format used for the debug statement 83 84 From a live system: 85 86 nullarbor:~ # cat <debugfs>/dynamic_debug/control 87 # filename:lineno [module]function flags format 88 fs/aio.c:222 [aio]__put_ioctx =_ "__put_ioctx:\040freeing\040%p\012" 89 fs/aio.c:248 [aio]ioctx_alloc =_ "ENOMEM:\040nr_events\040too\040high\012" 90 fs/aio.c:1770 [aio]sys_io_cancel =_ "calling\040cancel\012" 91 92 Example usage: 93 94 // enable the message at line 1603 of file svcsock.c 95 nullarbor:~ # echo -n 'file svcsock.c line 1603 +p' > 96 <debugfs>/dynamic_debug/control 97 98 // enable all the messages in file svcsock.c 99 nullarbor:~ # echo -n 'file svcsock.c +p' > 100 <debugfs>/dynamic_debug/control 101 102 // enable all the messages in the NFS server module 103 nullarbor:~ # echo -n 'module nfsd +p' > 104 <debugfs>/dynamic_debug/control 105 106 // enable all 12 messages in the function svc_process() 107 nullarbor:~ # echo -n 'func svc_process +p' > 108 <debugfs>/dynamic_debug/control 109 110 // disable all 12 messages in the function svc_process() 111 nullarbor:~ # echo -n 'func svc_process -p' > 112 <debugfs>/dynamic_debug/control 113 114 See Documentation/dynamic-debug-howto.txt for additional information. 115 116endmenu # "printk and dmesg options" 117 118menu "Compile-time checks and compiler options" 119 120config DEBUG_INFO 121 bool "Compile the kernel with debug info" 122 depends on DEBUG_KERNEL && !COMPILE_TEST 123 help 124 If you say Y here the resulting kernel image will include 125 debugging info resulting in a larger kernel image. 126 This adds debug symbols to the kernel and modules (gcc -g), and 127 is needed if you intend to use kernel crashdump or binary object 128 tools like crash, kgdb, LKCD, gdb, etc on the kernel. 129 Say Y here only if you plan to debug the kernel. 130 131 If unsure, say N. 132 133config DEBUG_INFO_REDUCED 134 bool "Reduce debugging information" 135 depends on DEBUG_INFO 136 help 137 If you say Y here gcc is instructed to generate less debugging 138 information for structure types. This means that tools that 139 need full debugging information (like kgdb or systemtap) won't 140 be happy. But if you merely need debugging information to 141 resolve line numbers there is no loss. Advantage is that 142 build directory object sizes shrink dramatically over a full 143 DEBUG_INFO build and compile times are reduced too. 144 Only works with newer gcc versions. 145 146config DEBUG_INFO_SPLIT 147 bool "Produce split debuginfo in .dwo files" 148 depends on DEBUG_INFO 149 help 150 Generate debug info into separate .dwo files. This significantly 151 reduces the build directory size for builds with DEBUG_INFO, 152 because it stores the information only once on disk in .dwo 153 files instead of multiple times in object files and executables. 154 In addition the debug information is also compressed. 155 156 Requires recent gcc (4.7+) and recent gdb/binutils. 157 Any tool that packages or reads debug information would need 158 to know about the .dwo files and include them. 159 Incompatible with older versions of ccache. 160 161config DEBUG_INFO_DWARF4 162 bool "Generate dwarf4 debuginfo" 163 depends on DEBUG_INFO 164 help 165 Generate dwarf4 debug info. This requires recent versions 166 of gcc and gdb. It makes the debug information larger. 167 But it significantly improves the success of resolving 168 variables in gdb on optimized code. 169 170config GDB_SCRIPTS 171 bool "Provide GDB scripts for kernel debugging" 172 depends on DEBUG_INFO 173 help 174 This creates the required links to GDB helper scripts in the 175 build directory. If you load vmlinux into gdb, the helper 176 scripts will be automatically imported by gdb as well, and 177 additional functions are available to analyze a Linux kernel 178 instance. See Documentation/gdb-kernel-debugging.txt for further 179 details. 180 181config ENABLE_WARN_DEPRECATED 182 bool "Enable __deprecated logic" 183 default y 184 help 185 Enable the __deprecated logic in the kernel build. 186 Disable this to suppress the "warning: 'foo' is deprecated 187 (declared at kernel/power/somefile.c:1234)" messages. 188 189config ENABLE_MUST_CHECK 190 bool "Enable __must_check logic" 191 default y 192 help 193 Enable the __must_check logic in the kernel build. Disable this to 194 suppress the "warning: ignoring return value of 'foo', declared with 195 attribute warn_unused_result" messages. 196 197config FRAME_WARN 198 int "Warn for stack frames larger than (needs gcc 4.4)" 199 range 0 8192 200 default 0 if KASAN 201 default 1024 if !64BIT 202 default 2048 if 64BIT 203 help 204 Tell gcc to warn at build time for stack frames larger than this. 205 Setting this too low will cause a lot of warnings. 206 Setting it to 0 disables the warning. 207 Requires gcc 4.4 208 209config STRIP_ASM_SYMS 210 bool "Strip assembler-generated symbols during link" 211 default n 212 help 213 Strip internal assembler-generated symbols during a link (symbols 214 that look like '.Lxxx') so they don't pollute the output of 215 get_wchan() and suchlike. 216 217config READABLE_ASM 218 bool "Generate readable assembler code" 219 depends on DEBUG_KERNEL 220 help 221 Disable some compiler optimizations that tend to generate human unreadable 222 assembler output. This may make the kernel slightly slower, but it helps 223 to keep kernel developers who have to stare a lot at assembler listings 224 sane. 225 226config UNUSED_SYMBOLS 227 bool "Enable unused/obsolete exported symbols" 228 default y if X86 229 help 230 Unused but exported symbols make the kernel needlessly bigger. For 231 that reason most of these unused exports will soon be removed. This 232 option is provided temporarily to provide a transition period in case 233 some external kernel module needs one of these symbols anyway. If you 234 encounter such a case in your module, consider if you are actually 235 using the right API. (rationale: since nobody in the kernel is using 236 this in a module, there is a pretty good chance it's actually the 237 wrong interface to use). If you really need the symbol, please send a 238 mail to the linux kernel mailing list mentioning the symbol and why 239 you really need it, and what the merge plan to the mainline kernel for 240 your module is. 241 242config PAGE_OWNER 243 bool "Track page owner" 244 depends on DEBUG_KERNEL && STACKTRACE_SUPPORT 245 select DEBUG_FS 246 select STACKTRACE 247 select PAGE_EXTENSION 248 help 249 This keeps track of what call chain is the owner of a page, may 250 help to find bare alloc_page(s) leaks. Even if you include this 251 feature on your build, it is disabled in default. You should pass 252 "page_owner=on" to boot parameter in order to enable it. Eats 253 a fair amount of memory if enabled. See tools/vm/page_owner_sort.c 254 for user-space helper. 255 256 If unsure, say N. 257 258config DEBUG_FS 259 bool "Debug Filesystem" 260 select SRCU 261 help 262 debugfs is a virtual file system that kernel developers use to put 263 debugging files into. Enable this option to be able to read and 264 write to these files. 265 266 For detailed documentation on the debugfs API, see 267 Documentation/DocBook/filesystems. 268 269 If unsure, say N. 270 271config HEADERS_CHECK 272 bool "Run 'make headers_check' when building vmlinux" 273 depends on !UML 274 help 275 This option will extract the user-visible kernel headers whenever 276 building the kernel, and will run basic sanity checks on them to 277 ensure that exported files do not attempt to include files which 278 were not exported, etc. 279 280 If you're making modifications to header files which are 281 relevant for userspace, say 'Y', and check the headers 282 exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in 283 your build tree), to make sure they're suitable. 284 285config DEBUG_SECTION_MISMATCH 286 bool "Enable full Section mismatch analysis" 287 help 288 The section mismatch analysis checks if there are illegal 289 references from one section to another section. 290 During linktime or runtime, some sections are dropped; 291 any use of code/data previously in these sections would 292 most likely result in an oops. 293 In the code, functions and variables are annotated with 294 __init,, etc. (see the full list in include/linux/init.h), 295 which results in the code/data being placed in specific sections. 296 The section mismatch analysis is always performed after a full 297 kernel build, and enabling this option causes the following 298 additional steps to occur: 299 - Add the option -fno-inline-functions-called-once to gcc commands. 300 When inlining a function annotated with __init in a non-init 301 function, we would lose the section information and thus 302 the analysis would not catch the illegal reference. 303 This option tells gcc to inline less (but it does result in 304 a larger kernel). 305 - Run the section mismatch analysis for each module/built-in.o file. 306 When we run the section mismatch analysis on vmlinux.o, we 307 lose valueble information about where the mismatch was 308 introduced. 309 Running the analysis for each module/built-in.o file 310 tells where the mismatch happens much closer to the 311 source. The drawback is that the same mismatch is 312 reported at least twice. 313 - Enable verbose reporting from modpost in order to help resolve 314 the section mismatches that are reported. 315 316config SECTION_MISMATCH_WARN_ONLY 317 bool "Make section mismatch errors non-fatal" 318 default y 319 help 320 If you say N here, the build process will fail if there are any 321 section mismatch, instead of just throwing warnings. 322 323 If unsure, say Y. 324 325# 326# Select this config option from the architecture Kconfig, if it 327# is preferred to always offer frame pointers as a config 328# option on the architecture (regardless of KERNEL_DEBUG): 329# 330config ARCH_WANT_FRAME_POINTERS 331 bool 332 help 333 334config FRAME_POINTER 335 bool "Compile the kernel with frame pointers" 336 depends on DEBUG_KERNEL && \ 337 (CRIS || M68K || FRV || UML || \ 338 AVR32 || SUPERH || BLACKFIN || MN10300 || METAG) || \ 339 ARCH_WANT_FRAME_POINTERS 340 default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS 341 help 342 If you say Y here the resulting kernel image will be slightly 343 larger and slower, but it gives very useful debugging information 344 in case of kernel bugs. (precise oopses/stacktraces/warnings) 345 346config STACK_VALIDATION 347 bool "Compile-time stack metadata validation" 348 depends on HAVE_STACK_VALIDATION 349 default n 350 help 351 Add compile-time checks to validate stack metadata, including frame 352 pointers (if CONFIG_FRAME_POINTER is enabled). This helps ensure 353 that runtime stack traces are more reliable. 354 355 For more information, see 356 tools/objtool/Documentation/stack-validation.txt. 357 358config DEBUG_FORCE_WEAK_PER_CPU 359 bool "Force weak per-cpu definitions" 360 depends on DEBUG_KERNEL 361 help 362 s390 and alpha require percpu variables in modules to be 363 defined weak to work around addressing range issue which 364 puts the following two restrictions on percpu variable 365 definitions. 366 367 1. percpu symbols must be unique whether static or not 368 2. percpu variables can't be defined inside a function 369 370 To ensure that generic code follows the above rules, this 371 option forces all percpu variables to be defined as weak. 372 373endmenu # "Compiler options" 374 375config MAGIC_SYSRQ 376 bool "Magic SysRq key" 377 depends on !UML 378 help 379 If you say Y here, you will have some control over the system even 380 if the system crashes for example during kernel debugging (e.g., you 381 will be able to flush the buffer cache to disk, reboot the system 382 immediately or dump some status information). This is accomplished 383 by pressing various keys while holding SysRq (Alt+PrintScreen). It 384 also works on a serial console (on PC hardware at least), if you 385 send a BREAK and then within 5 seconds a command keypress. The 386 keys are documented in <file:Documentation/sysrq.txt>. Don't say Y 387 unless you really know what this hack does. 388 389config MAGIC_SYSRQ_DEFAULT_ENABLE 390 hex "Enable magic SysRq key functions by default" 391 depends on MAGIC_SYSRQ 392 default 0x1 393 help 394 Specifies which SysRq key functions are enabled by default. 395 This may be set to 1 or 0 to enable or disable them all, or 396 to a bitmask as described in Documentation/sysrq.txt. 397 398config DEBUG_KERNEL 399 bool "Kernel debugging" 400 help 401 Say Y here if you are developing drivers or trying to debug and 402 identify kernel problems. 403 404menu "Memory Debugging" 405 406source mm/Kconfig.debug 407 408config DEBUG_OBJECTS 409 bool "Debug object operations" 410 depends on DEBUG_KERNEL 411 help 412 If you say Y here, additional code will be inserted into the 413 kernel to track the life time of various objects and validate 414 the operations on those objects. 415 416config DEBUG_OBJECTS_SELFTEST 417 bool "Debug objects selftest" 418 depends on DEBUG_OBJECTS 419 help 420 This enables the selftest of the object debug code. 421 422config DEBUG_OBJECTS_FREE 423 bool "Debug objects in freed memory" 424 depends on DEBUG_OBJECTS 425 help 426 This enables checks whether a k/v free operation frees an area 427 which contains an object which has not been deactivated 428 properly. This can make kmalloc/kfree-intensive workloads 429 much slower. 430 431config DEBUG_OBJECTS_TIMERS 432 bool "Debug timer objects" 433 depends on DEBUG_OBJECTS 434 help 435 If you say Y here, additional code will be inserted into the 436 timer routines to track the life time of timer objects and 437 validate the timer operations. 438 439config DEBUG_OBJECTS_WORK 440 bool "Debug work objects" 441 depends on DEBUG_OBJECTS 442 help 443 If you say Y here, additional code will be inserted into the 444 work queue routines to track the life time of work objects and 445 validate the work operations. 446 447config DEBUG_OBJECTS_RCU_HEAD 448 bool "Debug RCU callbacks objects" 449 depends on DEBUG_OBJECTS 450 help 451 Enable this to turn on debugging of RCU list heads (call_rcu() usage). 452 453config DEBUG_OBJECTS_PERCPU_COUNTER 454 bool "Debug percpu counter objects" 455 depends on DEBUG_OBJECTS 456 help 457 If you say Y here, additional code will be inserted into the 458 percpu counter routines to track the life time of percpu counter 459 objects and validate the percpu counter operations. 460 461config DEBUG_OBJECTS_ENABLE_DEFAULT 462 int "debug_objects bootup default value (0-1)" 463 range 0 1 464 default "1" 465 depends on DEBUG_OBJECTS 466 help 467 Debug objects boot parameter default value 468 469config DEBUG_SLAB 470 bool "Debug slab memory allocations" 471 depends on DEBUG_KERNEL && SLAB && !KMEMCHECK 472 help 473 Say Y here to have the kernel do limited verification on memory 474 allocation as well as poisoning memory on free to catch use of freed 475 memory. This can make kmalloc/kfree-intensive workloads much slower. 476 477config DEBUG_SLAB_LEAK 478 bool "Memory leak debugging" 479 depends on DEBUG_SLAB 480 481config SLUB_DEBUG_ON 482 bool "SLUB debugging on by default" 483 depends on SLUB && SLUB_DEBUG && !KMEMCHECK 484 default n 485 help 486 Boot with debugging on by default. SLUB boots by default with 487 the runtime debug capabilities switched off. Enabling this is 488 equivalent to specifying the "slub_debug" parameter on boot. 489 There is no support for more fine grained debug control like 490 possible with slub_debug=xxx. SLUB debugging may be switched 491 off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying 492 "slub_debug=-". 493 494config SLUB_STATS 495 default n 496 bool "Enable SLUB performance statistics" 497 depends on SLUB && SYSFS 498 help 499 SLUB statistics are useful to debug SLUBs allocation behavior in 500 order find ways to optimize the allocator. This should never be 501 enabled for production use since keeping statistics slows down 502 the allocator by a few percentage points. The slabinfo command 503 supports the determination of the most active slabs to figure 504 out which slabs are relevant to a particular load. 505 Try running: slabinfo -DA 506 507config HAVE_DEBUG_KMEMLEAK 508 bool 509 510config DEBUG_KMEMLEAK 511 bool "Kernel memory leak detector" 512 depends on DEBUG_KERNEL && HAVE_DEBUG_KMEMLEAK 513 select DEBUG_FS 514 select STACKTRACE if STACKTRACE_SUPPORT 515 select KALLSYMS 516 select CRC32 517 help 518 Say Y here if you want to enable the memory leak 519 detector. The memory allocation/freeing is traced in a way 520 similar to the Boehm's conservative garbage collector, the 521 difference being that the orphan objects are not freed but 522 only shown in /sys/kernel/debug/kmemleak. Enabling this 523 feature will introduce an overhead to memory 524 allocations. See Documentation/kmemleak.txt for more 525 details. 526 527 Enabling DEBUG_SLAB or SLUB_DEBUG may increase the chances 528 of finding leaks due to the slab objects poisoning. 529 530 In order to access the kmemleak file, debugfs needs to be 531 mounted (usually at /sys/kernel/debug). 532 533config DEBUG_KMEMLEAK_EARLY_LOG_SIZE 534 int "Maximum kmemleak early log entries" 535 depends on DEBUG_KMEMLEAK 536 range 200 40000 537 default 400 538 help 539 Kmemleak must track all the memory allocations to avoid 540 reporting false positives. Since memory may be allocated or 541 freed before kmemleak is initialised, an early log buffer is 542 used to store these actions. If kmemleak reports "early log 543 buffer exceeded", please increase this value. 544 545config DEBUG_KMEMLEAK_TEST 546 tristate "Simple test for the kernel memory leak detector" 547 depends on DEBUG_KMEMLEAK && m 548 help 549 This option enables a module that explicitly leaks memory. 550 551 If unsure, say N. 552 553config DEBUG_KMEMLEAK_DEFAULT_OFF 554 bool "Default kmemleak to off" 555 depends on DEBUG_KMEMLEAK 556 help 557 Say Y here to disable kmemleak by default. It can then be enabled 558 on the command line via kmemleak=on. 559 560config DEBUG_STACK_USAGE 561 bool "Stack utilization instrumentation" 562 depends on DEBUG_KERNEL && !IA64 563 help 564 Enables the display of the minimum amount of free stack which each 565 task has ever had available in the sysrq-T and sysrq-P debug output. 566 567 This option will slow down process creation somewhat. 568 569config DEBUG_VM 570 bool "Debug VM" 571 depends on DEBUG_KERNEL 572 help 573 Enable this to turn on extended checks in the virtual-memory system 574 that may impact performance. 575 576 If unsure, say N. 577 578config DEBUG_VM_VMACACHE 579 bool "Debug VMA caching" 580 depends on DEBUG_VM 581 help 582 Enable this to turn on VMA caching debug information. Doing so 583 can cause significant overhead, so only enable it in non-production 584 environments. 585 586 If unsure, say N. 587 588config DEBUG_VM_RB 589 bool "Debug VM red-black trees" 590 depends on DEBUG_VM 591 help 592 Enable VM red-black tree debugging information and extra validations. 593 594 If unsure, say N. 595 596config DEBUG_VM_PGFLAGS 597 bool "Debug page-flags operations" 598 depends on DEBUG_VM 599 help 600 Enables extra validation on page flags operations. 601 602 If unsure, say N. 603 604config DEBUG_VIRTUAL 605 bool "Debug VM translations" 606 depends on DEBUG_KERNEL && X86 607 help 608 Enable some costly sanity checks in virtual to page code. This can 609 catch mistakes with virt_to_page() and friends. 610 611 If unsure, say N. 612 613config DEBUG_NOMMU_REGIONS 614 bool "Debug the global anon/private NOMMU mapping region tree" 615 depends on DEBUG_KERNEL && !MMU 616 help 617 This option causes the global tree of anonymous and private mapping 618 regions to be regularly checked for invalid topology. 619 620config DEBUG_MEMORY_INIT 621 bool "Debug memory initialisation" if EXPERT 622 default !EXPERT 623 help 624 Enable this for additional checks during memory initialisation. 625 The sanity checks verify aspects of the VM such as the memory model 626 and other information provided by the architecture. Verbose 627 information will be printed at KERN_DEBUG loglevel depending 628 on the mminit_loglevel= command-line option. 629 630 If unsure, say Y 631 632config MEMORY_NOTIFIER_ERROR_INJECT 633 tristate "Memory hotplug notifier error injection module" 634 depends on MEMORY_HOTPLUG_SPARSE && NOTIFIER_ERROR_INJECTION 635 help 636 This option provides the ability to inject artificial errors to 637 memory hotplug notifier chain callbacks. It is controlled through 638 debugfs interface under /sys/kernel/debug/notifier-error-inject/memory 639 640 If the notifier call chain should be failed with some events 641 notified, write the error code to "actions/<notifier event>/error". 642 643 Example: Inject memory hotplug offline error (-12 == -ENOMEM) 644 645 # cd /sys/kernel/debug/notifier-error-inject/memory 646 # echo -12 > actions/MEM_GOING_OFFLINE/error 647 # echo offline > /sys/devices/system/memory/memoryXXX/state 648 bash: echo: write error: Cannot allocate memory 649 650 To compile this code as a module, choose M here: the module will 651 be called memory-notifier-error-inject. 652 653 If unsure, say N. 654 655config DEBUG_PER_CPU_MAPS 656 bool "Debug access to per_cpu maps" 657 depends on DEBUG_KERNEL 658 depends on SMP 659 help 660 Say Y to verify that the per_cpu map being accessed has 661 been set up. This adds a fair amount of code to kernel memory 662 and decreases performance. 663 664 Say N if unsure. 665 666config DEBUG_HIGHMEM 667 bool "Highmem debugging" 668 depends on DEBUG_KERNEL && HIGHMEM 669 help 670 This option enables additional error checking for high memory 671 systems. Disable for production systems. 672 673config HAVE_DEBUG_STACKOVERFLOW 674 bool 675 676config DEBUG_STACKOVERFLOW 677 bool "Check for stack overflows" 678 depends on DEBUG_KERNEL && HAVE_DEBUG_STACKOVERFLOW 679 ---help--- 680 Say Y here if you want to check for overflows of kernel, IRQ 681 and exception stacks (if your architecture uses them). This 682 option will show detailed messages if free stack space drops 683 below a certain limit. 684 685 These kinds of bugs usually occur when call-chains in the 686 kernel get too deep, especially when interrupts are 687 involved. 688 689 Use this in cases where you see apparently random memory 690 corruption, especially if it appears in 'struct thread_info' 691 692 If in doubt, say "N". 693 694source "lib/Kconfig.kmemcheck" 695 696source "lib/Kconfig.kasan" 697 698endmenu # "Memory Debugging" 699 700config ARCH_HAS_KCOV 701 bool 702 help 703 KCOV does not have any arch-specific code, but currently it is enabled 704 only for x86_64. KCOV requires testing on other archs, and most likely 705 disabling of instrumentation for some early boot code. 706 707config KCOV 708 bool "Code coverage for fuzzing" 709 depends on ARCH_HAS_KCOV 710 select DEBUG_FS 711 help 712 KCOV exposes kernel code coverage information in a form suitable 713 for coverage-guided fuzzing (randomized testing). 714 715 If RANDOMIZE_BASE is enabled, PC values will not be stable across 716 different machines and across reboots. If you need stable PC values, 717 disable RANDOMIZE_BASE. 718 719 For more details, see Documentation/kcov.txt. 720 721config DEBUG_SHIRQ 722 bool "Debug shared IRQ handlers" 723 depends on DEBUG_KERNEL 724 help 725 Enable this to generate a spurious interrupt as soon as a shared 726 interrupt handler is registered, and just before one is deregistered. 727 Drivers ought to be able to handle interrupts coming in at those 728 points; some don't and need to be caught. 729 730menu "Debug Lockups and Hangs" 731 732config LOCKUP_DETECTOR 733 bool "Detect Hard and Soft Lockups" 734 depends on DEBUG_KERNEL && !S390 735 help 736 Say Y here to enable the kernel to act as a watchdog to detect 737 hard and soft lockups. 738 739 Softlockups are bugs that cause the kernel to loop in kernel 740 mode for more than 20 seconds, without giving other tasks a 741 chance to run. The current stack trace is displayed upon 742 detection and the system will stay locked up. 743 744 Hardlockups are bugs that cause the CPU to loop in kernel mode 745 for more than 10 seconds, without letting other interrupts have a 746 chance to run. The current stack trace is displayed upon detection 747 and the system will stay locked up. 748 749 The overhead should be minimal. A periodic hrtimer runs to 750 generate interrupts and kick the watchdog task every 4 seconds. 751 An NMI is generated every 10 seconds or so to check for hardlockups. 752 753 The frequency of hrtimer and NMI events and the soft and hard lockup 754 thresholds can be controlled through the sysctl watchdog_thresh. 755 756config HARDLOCKUP_DETECTOR 757 def_bool y 758 depends on LOCKUP_DETECTOR && !HAVE_NMI_WATCHDOG 759 depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI 760 761config BOOTPARAM_HARDLOCKUP_PANIC 762 bool "Panic (Reboot) On Hard Lockups" 763 depends on HARDLOCKUP_DETECTOR 764 help 765 Say Y here to enable the kernel to panic on "hard lockups", 766 which are bugs that cause the kernel to loop in kernel 767 mode with interrupts disabled for more than 10 seconds (configurable 768 using the watchdog_thresh sysctl). 769 770 Say N if unsure. 771 772config BOOTPARAM_HARDLOCKUP_PANIC_VALUE 773 int 774 depends on HARDLOCKUP_DETECTOR 775 range 0 1 776 default 0 if !BOOTPARAM_HARDLOCKUP_PANIC 777 default 1 if BOOTPARAM_HARDLOCKUP_PANIC 778 779config BOOTPARAM_SOFTLOCKUP_PANIC 780 bool "Panic (Reboot) On Soft Lockups" 781 depends on LOCKUP_DETECTOR 782 help 783 Say Y here to enable the kernel to panic on "soft lockups", 784 which are bugs that cause the kernel to loop in kernel 785 mode for more than 20 seconds (configurable using the watchdog_thresh 786 sysctl), without giving other tasks a chance to run. 787 788 The panic can be used in combination with panic_timeout, 789 to cause the system to reboot automatically after a 790 lockup has been detected. This feature is useful for 791 high-availability systems that have uptime guarantees and 792 where a lockup must be resolved ASAP. 793 794 Say N if unsure. 795 796config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE 797 int 798 depends on LOCKUP_DETECTOR 799 range 0 1 800 default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC 801 default 1 if BOOTPARAM_SOFTLOCKUP_PANIC 802 803config DETECT_HUNG_TASK 804 bool "Detect Hung Tasks" 805 depends on DEBUG_KERNEL 806 default LOCKUP_DETECTOR 807 help 808 Say Y here to enable the kernel to detect "hung tasks", 809 which are bugs that cause the task to be stuck in 810 uninterruptible "D" state indefinitiley. 811 812 When a hung task is detected, the kernel will print the 813 current stack trace (which you should report), but the 814 task will stay in uninterruptible state. If lockdep is 815 enabled then all held locks will also be reported. This 816 feature has negligible overhead. 817 818config DEFAULT_HUNG_TASK_TIMEOUT 819 int "Default timeout for hung task detection (in seconds)" 820 depends on DETECT_HUNG_TASK 821 default 120 822 help 823 This option controls the default timeout (in seconds) used 824 to determine when a task has become non-responsive and should 825 be considered hung. 826 827 It can be adjusted at runtime via the kernel.hung_task_timeout_secs 828 sysctl or by writing a value to 829 /proc/sys/kernel/hung_task_timeout_secs. 830 831 A timeout of 0 disables the check. The default is two minutes. 832 Keeping the default should be fine in most cases. 833 834config BOOTPARAM_HUNG_TASK_PANIC 835 bool "Panic (Reboot) On Hung Tasks" 836 depends on DETECT_HUNG_TASK 837 help 838 Say Y here to enable the kernel to panic on "hung tasks", 839 which are bugs that cause the kernel to leave a task stuck 840 in uninterruptible "D" state. 841 842 The panic can be used in combination with panic_timeout, 843 to cause the system to reboot automatically after a 844 hung task has been detected. This feature is useful for 845 high-availability systems that have uptime guarantees and 846 where a hung tasks must be resolved ASAP. 847 848 Say N if unsure. 849 850config BOOTPARAM_HUNG_TASK_PANIC_VALUE 851 int 852 depends on DETECT_HUNG_TASK 853 range 0 1 854 default 0 if !BOOTPARAM_HUNG_TASK_PANIC 855 default 1 if BOOTPARAM_HUNG_TASK_PANIC 856 857config WQ_WATCHDOG 858 bool "Detect Workqueue Stalls" 859 depends on DEBUG_KERNEL 860 help 861 Say Y here to enable stall detection on workqueues. If a 862 worker pool doesn't make forward progress on a pending work 863 item for over a given amount of time, 30s by default, a 864 warning message is printed along with dump of workqueue 865 state. This can be configured through kernel parameter 866 "workqueue.watchdog_thresh" and its sysfs counterpart. 867 868endmenu # "Debug lockups and hangs" 869 870config PANIC_ON_OOPS 871 bool "Panic on Oops" 872 help 873 Say Y here to enable the kernel to panic when it oopses. This 874 has the same effect as setting oops=panic on the kernel command 875 line. 876 877 This feature is useful to ensure that the kernel does not do 878 anything erroneous after an oops which could result in data 879 corruption or other issues. 880 881 Say N if unsure. 882 883config PANIC_ON_OOPS_VALUE 884 int 885 range 0 1 886 default 0 if !PANIC_ON_OOPS 887 default 1 if PANIC_ON_OOPS 888 889config PANIC_TIMEOUT 890 int "panic timeout" 891 default 0 892 help 893 Set the timeout value (in seconds) until a reboot occurs when the 894 the kernel panics. If n = 0, then we wait forever. A timeout 895 value n > 0 will wait n seconds before rebooting, while a timeout 896 value n < 0 will reboot immediately. 897 898config SCHED_DEBUG 899 bool "Collect scheduler debugging info" 900 depends on DEBUG_KERNEL && PROC_FS 901 default y 902 help 903 If you say Y here, the /proc/sched_debug file will be provided 904 that can help debug the scheduler. The runtime overhead of this 905 option is minimal. 906 907config SCHED_INFO 908 bool 909 default n 910 911config SCHEDSTATS 912 bool "Collect scheduler statistics" 913 depends on DEBUG_KERNEL && PROC_FS 914 select SCHED_INFO 915 help 916 If you say Y here, additional code will be inserted into the 917 scheduler and related routines to collect statistics about 918 scheduler behavior and provide them in /proc/schedstat. These 919 stats may be useful for both tuning and debugging the scheduler 920 If you aren't debugging the scheduler or trying to tune a specific 921 application, you can say N to avoid the very slight overhead 922 this adds. 923 924config SCHED_STACK_END_CHECK 925 bool "Detect stack corruption on calls to schedule()" 926 depends on DEBUG_KERNEL 927 default n 928 help 929 This option checks for a stack overrun on calls to schedule(). 930 If the stack end location is found to be over written always panic as 931 the content of the corrupted region can no longer be trusted. 932 This is to ensure no erroneous behaviour occurs which could result in 933 data corruption or a sporadic crash at a later stage once the region 934 is examined. The runtime overhead introduced is minimal. 935 936config DEBUG_TIMEKEEPING 937 bool "Enable extra timekeeping sanity checking" 938 help 939 This option will enable additional timekeeping sanity checks 940 which may be helpful when diagnosing issues where timekeeping 941 problems are suspected. 942 943 This may include checks in the timekeeping hotpaths, so this 944 option may have a (very small) performance impact to some 945 workloads. 946 947 If unsure, say N. 948 949config TIMER_STATS 950 bool "Collect kernel timers statistics" 951 depends on DEBUG_KERNEL && PROC_FS 952 help 953 If you say Y here, additional code will be inserted into the 954 timer routines to collect statistics about kernel timers being 955 reprogrammed. The statistics can be read from /proc/timer_stats. 956 The statistics collection is started by writing 1 to /proc/timer_stats, 957 writing 0 stops it. This feature is useful to collect information 958 about timer usage patterns in kernel and userspace. This feature 959 is lightweight if enabled in the kernel config but not activated 960 (it defaults to deactivated on bootup and will only be activated 961 if some application like powertop activates it explicitly). 962 963config DEBUG_PREEMPT 964 bool "Debug preemptible kernel" 965 depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT 966 default y 967 help 968 If you say Y here then the kernel will use a debug variant of the 969 commonly used smp_processor_id() function and will print warnings 970 if kernel code uses it in a preemption-unsafe way. Also, the kernel 971 will detect preemption count underflows. 972 973menu "Lock Debugging (spinlocks, mutexes, etc...)" 974 975config DEBUG_RT_MUTEXES 976 bool "RT Mutex debugging, deadlock detection" 977 depends on DEBUG_KERNEL && RT_MUTEXES 978 help 979 This allows rt mutex semantics violations and rt mutex related 980 deadlocks (lockups) to be detected and reported automatically. 981 982config DEBUG_SPINLOCK 983 bool "Spinlock and rw-lock debugging: basic checks" 984 depends on DEBUG_KERNEL 985 select UNINLINE_SPIN_UNLOCK 986 help 987 Say Y here and build SMP to catch missing spinlock initialization 988 and certain other kinds of spinlock errors commonly made. This is 989 best used in conjunction with the NMI watchdog so that spinlock 990 deadlocks are also debuggable. 991 992config DEBUG_MUTEXES 993 bool "Mutex debugging: basic checks" 994 depends on DEBUG_KERNEL 995 help 996 This feature allows mutex semantics violations to be detected and 997 reported. 998 999config DEBUG_WW_MUTEX_SLOWPATH 1000 bool "Wait/wound mutex debugging: Slowpath testing" 1001 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1002 select DEBUG_LOCK_ALLOC 1003 select DEBUG_SPINLOCK 1004 select DEBUG_MUTEXES 1005 help 1006 This feature enables slowpath testing for w/w mutex users by 1007 injecting additional -EDEADLK wound/backoff cases. Together with 1008 the full mutex checks enabled with (CONFIG_PROVE_LOCKING) this 1009 will test all possible w/w mutex interface abuse with the 1010 exception of simply not acquiring all the required locks. 1011 Note that this feature can introduce significant overhead, so 1012 it really should not be enabled in a production or distro kernel, 1013 even a debug kernel. If you are a driver writer, enable it. If 1014 you are a distro, do not. 1015 1016config DEBUG_LOCK_ALLOC 1017 bool "Lock debugging: detect incorrect freeing of live locks" 1018 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1019 select DEBUG_SPINLOCK 1020 select DEBUG_MUTEXES 1021 select LOCKDEP 1022 help 1023 This feature will check whether any held lock (spinlock, rwlock, 1024 mutex or rwsem) is incorrectly freed by the kernel, via any of the 1025 memory-freeing routines (kfree(), kmem_cache_free(), free_pages(), 1026 vfree(), etc.), whether a live lock is incorrectly reinitialized via 1027 spin_lock_init()/mutex_init()/etc., or whether there is any lock 1028 held during task exit. 1029 1030config PROVE_LOCKING 1031 bool "Lock debugging: prove locking correctness" 1032 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1033 select LOCKDEP 1034 select DEBUG_SPINLOCK 1035 select DEBUG_MUTEXES 1036 select DEBUG_LOCK_ALLOC 1037 select TRACE_IRQFLAGS 1038 default n 1039 help 1040 This feature enables the kernel to prove that all locking 1041 that occurs in the kernel runtime is mathematically 1042 correct: that under no circumstance could an arbitrary (and 1043 not yet triggered) combination of observed locking 1044 sequences (on an arbitrary number of CPUs, running an 1045 arbitrary number of tasks and interrupt contexts) cause a 1046 deadlock. 1047 1048 In short, this feature enables the kernel to report locking 1049 related deadlocks before they actually occur. 1050 1051 The proof does not depend on how hard and complex a 1052 deadlock scenario would be to trigger: how many 1053 participant CPUs, tasks and irq-contexts would be needed 1054 for it to trigger. The proof also does not depend on 1055 timing: if a race and a resulting deadlock is possible 1056 theoretically (no matter how unlikely the race scenario 1057 is), it will be proven so and will immediately be 1058 reported by the kernel (once the event is observed that 1059 makes the deadlock theoretically possible). 1060 1061 If a deadlock is impossible (i.e. the locking rules, as 1062 observed by the kernel, are mathematically correct), the 1063 kernel reports nothing. 1064 1065 NOTE: this feature can also be enabled for rwlocks, mutexes 1066 and rwsems - in which case all dependencies between these 1067 different locking variants are observed and mapped too, and 1068 the proof of observed correctness is also maintained for an 1069 arbitrary combination of these separate locking variants. 1070 1071 For more details, see Documentation/locking/lockdep-design.txt. 1072 1073config LOCKDEP 1074 bool 1075 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1076 select STACKTRACE 1077 select FRAME_POINTER if !MIPS && !PPC && !ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !SCORE 1078 select KALLSYMS 1079 select KALLSYMS_ALL 1080 1081config LOCK_STAT 1082 bool "Lock usage statistics" 1083 depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT 1084 select LOCKDEP 1085 select DEBUG_SPINLOCK 1086 select DEBUG_MUTEXES 1087 select DEBUG_LOCK_ALLOC 1088 default n 1089 help 1090 This feature enables tracking lock contention points 1091 1092 For more details, see Documentation/locking/lockstat.txt 1093 1094 This also enables lock events required by "perf lock", 1095 subcommand of perf. 1096 If you want to use "perf lock", you also need to turn on 1097 CONFIG_EVENT_TRACING. 1098 1099 CONFIG_LOCK_STAT defines "contended" and "acquired" lock events. 1100 (CONFIG_LOCKDEP defines "acquire" and "release" events.) 1101 1102config DEBUG_LOCKDEP 1103 bool "Lock dependency engine debugging" 1104 depends on DEBUG_KERNEL && LOCKDEP 1105 help 1106 If you say Y here, the lock dependency engine will do 1107 additional runtime checks to debug itself, at the price 1108 of more runtime overhead. 1109 1110config DEBUG_ATOMIC_SLEEP 1111 bool "Sleep inside atomic section checking" 1112 select PREEMPT_COUNT 1113 depends on DEBUG_KERNEL 1114 help 1115 If you say Y here, various routines which may sleep will become very 1116 noisy if they are called inside atomic sections: when a spinlock is 1117 held, inside an rcu read side critical section, inside preempt disabled 1118 sections, inside an interrupt, etc... 1119 1120config DEBUG_LOCKING_API_SELFTESTS 1121 bool "Locking API boot-time self-tests" 1122 depends on DEBUG_KERNEL 1123 help 1124 Say Y here if you want the kernel to run a short self-test during 1125 bootup. The self-test checks whether common types of locking bugs 1126 are detected by debugging mechanisms or not. (if you disable 1127 lock debugging then those bugs wont be detected of course.) 1128 The following locking APIs are covered: spinlocks, rwlocks, 1129 mutexes and rwsems. 1130 1131config LOCK_TORTURE_TEST 1132 tristate "torture tests for locking" 1133 depends on DEBUG_KERNEL 1134 select TORTURE_TEST 1135 default n 1136 help 1137 This option provides a kernel module that runs torture tests 1138 on kernel locking primitives. The kernel module may be built 1139 after the fact on the running kernel to be tested, if desired. 1140 1141 Say Y here if you want kernel locking-primitive torture tests 1142 to be built into the kernel. 1143 Say M if you want these torture tests to build as a module. 1144 Say N if you are unsure. 1145 1146endmenu # lock debugging 1147 1148config TRACE_IRQFLAGS 1149 bool 1150 help 1151 Enables hooks to interrupt enabling and disabling for 1152 either tracing or lock debugging. 1153 1154config STACKTRACE 1155 bool "Stack backtrace support" 1156 depends on STACKTRACE_SUPPORT 1157 help 1158 This option causes the kernel to create a /proc/pid/stack for 1159 every process, showing its current stack trace. 1160 It is also used by various kernel debugging features that require 1161 stack trace generation. 1162 1163config DEBUG_KOBJECT 1164 bool "kobject debugging" 1165 depends on DEBUG_KERNEL 1166 help 1167 If you say Y here, some extra kobject debugging messages will be sent 1168 to the syslog. 1169 1170config DEBUG_KOBJECT_RELEASE 1171 bool "kobject release debugging" 1172 depends on DEBUG_OBJECTS_TIMERS 1173 help 1174 kobjects are reference counted objects. This means that their 1175 last reference count put is not predictable, and the kobject can 1176 live on past the point at which a driver decides to drop it's 1177 initial reference to the kobject gained on allocation. An 1178 example of this would be a struct device which has just been 1179 unregistered. 1180 1181 However, some buggy drivers assume that after such an operation, 1182 the memory backing the kobject can be immediately freed. This 1183 goes completely against the principles of a refcounted object. 1184 1185 If you say Y here, the kernel will delay the release of kobjects 1186 on the last reference count to improve the visibility of this 1187 kind of kobject release bug. 1188 1189config HAVE_DEBUG_BUGVERBOSE 1190 bool 1191 1192config DEBUG_BUGVERBOSE 1193 bool "Verbose BUG() reporting (adds 70K)" if DEBUG_KERNEL && EXPERT 1194 depends on BUG && (GENERIC_BUG || HAVE_DEBUG_BUGVERBOSE) 1195 default y 1196 help 1197 Say Y here to make BUG() panics output the file name and line number 1198 of the BUG call as well as the EIP and oops trace. This aids 1199 debugging but costs about 70-100K of memory. 1200 1201config DEBUG_LIST 1202 bool "Debug linked list manipulation" 1203 depends on DEBUG_KERNEL 1204 help 1205 Enable this to turn on extended checks in the linked-list 1206 walking routines. 1207 1208 If unsure, say N. 1209 1210config DEBUG_PI_LIST 1211 bool "Debug priority linked list manipulation" 1212 depends on DEBUG_KERNEL 1213 help 1214 Enable this to turn on extended checks in the priority-ordered 1215 linked-list (plist) walking routines. This checks the entire 1216 list multiple times during each manipulation. 1217 1218 If unsure, say N. 1219 1220config DEBUG_SG 1221 bool "Debug SG table operations" 1222 depends on DEBUG_KERNEL 1223 help 1224 Enable this to turn on checks on scatter-gather tables. This can 1225 help find problems with drivers that do not properly initialize 1226 their sg tables. 1227 1228 If unsure, say N. 1229 1230config DEBUG_NOTIFIERS 1231 bool "Debug notifier call chains" 1232 depends on DEBUG_KERNEL 1233 help 1234 Enable this to turn on sanity checking for notifier call chains. 1235 This is most useful for kernel developers to make sure that 1236 modules properly unregister themselves from notifier chains. 1237 This is a relatively cheap check but if you care about maximum 1238 performance, say N. 1239 1240config DEBUG_CREDENTIALS 1241 bool "Debug credential management" 1242 depends on DEBUG_KERNEL 1243 help 1244 Enable this to turn on some debug checking for credential 1245 management. The additional code keeps track of the number of 1246 pointers from task_structs to any given cred struct, and checks to 1247 see that this number never exceeds the usage count of the cred 1248 struct. 1249 1250 Furthermore, if SELinux is enabled, this also checks that the 1251 security pointer in the cred struct is never seen to be invalid. 1252 1253 If unsure, say N. 1254 1255menu "RCU Debugging" 1256 1257config PROVE_RCU 1258 def_bool PROVE_LOCKING 1259 1260config PROVE_RCU_REPEATEDLY 1261 bool "RCU debugging: don't disable PROVE_RCU on first splat" 1262 depends on PROVE_RCU 1263 default n 1264 help 1265 By itself, PROVE_RCU will disable checking upon issuing the 1266 first warning (or "splat"). This feature prevents such 1267 disabling, allowing multiple RCU-lockdep warnings to be printed 1268 on a single reboot. 1269 1270 Say Y to allow multiple RCU-lockdep warnings per boot. 1271 1272 Say N if you are unsure. 1273 1274config SPARSE_RCU_POINTER 1275 bool "RCU debugging: sparse-based checks for pointer usage" 1276 default n 1277 help 1278 This feature enables the __rcu sparse annotation for 1279 RCU-protected pointers. This annotation will cause sparse 1280 to flag any non-RCU used of annotated pointers. This can be 1281 helpful when debugging RCU usage. Please note that this feature 1282 is not intended to enforce code cleanliness; it is instead merely 1283 a debugging aid. 1284 1285 Say Y to make sparse flag questionable use of RCU-protected pointers 1286 1287 Say N if you are unsure. 1288 1289config TORTURE_TEST 1290 tristate 1291 default n 1292 1293config RCU_PERF_TEST 1294 tristate "performance tests for RCU" 1295 depends on DEBUG_KERNEL 1296 select TORTURE_TEST 1297 select SRCU 1298 select TASKS_RCU 1299 default n 1300 help 1301 This option provides a kernel module that runs performance 1302 tests on the RCU infrastructure. The kernel module may be built 1303 after the fact on the running kernel to be tested, if desired. 1304 1305 Say Y here if you want RCU performance tests to be built into 1306 the kernel. 1307 Say M if you want the RCU performance tests to build as a module. 1308 Say N if you are unsure. 1309 1310config RCU_PERF_TEST_RUNNABLE 1311 bool "performance tests for RCU runnable by default" 1312 depends on RCU_PERF_TEST = y 1313 default n 1314 help 1315 This option provides a way to build the RCU performance tests 1316 directly into the kernel without them starting up at boot time. 1317 You can use /sys/module to manually override this setting. 1318 This /proc file is available only when the RCU performance 1319 tests have been built into the kernel. 1320 1321 Say Y here if you want the RCU performance tests to start during 1322 boot (you probably don't). 1323 Say N here if you want the RCU performance tests to start only 1324 after being manually enabled via /sys/module. 1325 1326config RCU_TORTURE_TEST 1327 tristate "torture tests for RCU" 1328 depends on DEBUG_KERNEL 1329 select TORTURE_TEST 1330 select SRCU 1331 select TASKS_RCU 1332 default n 1333 help 1334 This option provides a kernel module that runs torture tests 1335 on the RCU infrastructure. The kernel module may be built 1336 after the fact on the running kernel to be tested, if desired. 1337 1338 Say Y here if you want RCU torture tests to be built into 1339 the kernel. 1340 Say M if you want the RCU torture tests to build as a module. 1341 Say N if you are unsure. 1342 1343config RCU_TORTURE_TEST_RUNNABLE 1344 bool "torture tests for RCU runnable by default" 1345 depends on RCU_TORTURE_TEST = y 1346 default n 1347 help 1348 This option provides a way to build the RCU torture tests 1349 directly into the kernel without them starting up at boot 1350 time. You can use /proc/sys/kernel/rcutorture_runnable 1351 to manually override this setting. This /proc file is 1352 available only when the RCU torture tests have been built 1353 into the kernel. 1354 1355 Say Y here if you want the RCU torture tests to start during 1356 boot (you probably don't). 1357 Say N here if you want the RCU torture tests to start only 1358 after being manually enabled via /proc. 1359 1360config RCU_TORTURE_TEST_SLOW_PREINIT 1361 bool "Slow down RCU grace-period pre-initialization to expose races" 1362 depends on RCU_TORTURE_TEST 1363 help 1364 This option delays grace-period pre-initialization (the 1365 propagation of CPU-hotplug changes up the rcu_node combining 1366 tree) for a few jiffies between initializing each pair of 1367 consecutive rcu_node structures. This helps to expose races 1368 involving grace-period pre-initialization, in other words, it 1369 makes your kernel less stable. It can also greatly increase 1370 grace-period latency, especially on systems with large numbers 1371 of CPUs. This is useful when torture-testing RCU, but in 1372 almost no other circumstance. 1373 1374 Say Y here if you want your system to crash and hang more often. 1375 Say N if you want a sane system. 1376 1377config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY 1378 int "How much to slow down RCU grace-period pre-initialization" 1379 range 0 5 1380 default 3 1381 depends on RCU_TORTURE_TEST_SLOW_PREINIT 1382 help 1383 This option specifies the number of jiffies to wait between 1384 each rcu_node structure pre-initialization step. 1385 1386config RCU_TORTURE_TEST_SLOW_INIT 1387 bool "Slow down RCU grace-period initialization to expose races" 1388 depends on RCU_TORTURE_TEST 1389 help 1390 This option delays grace-period initialization for a few 1391 jiffies between initializing each pair of consecutive 1392 rcu_node structures. This helps to expose races involving 1393 grace-period initialization, in other words, it makes your 1394 kernel less stable. It can also greatly increase grace-period 1395 latency, especially on systems with large numbers of CPUs. 1396 This is useful when torture-testing RCU, but in almost no 1397 other circumstance. 1398 1399 Say Y here if you want your system to crash and hang more often. 1400 Say N if you want a sane system. 1401 1402config RCU_TORTURE_TEST_SLOW_INIT_DELAY 1403 int "How much to slow down RCU grace-period initialization" 1404 range 0 5 1405 default 3 1406 depends on RCU_TORTURE_TEST_SLOW_INIT 1407 help 1408 This option specifies the number of jiffies to wait between 1409 each rcu_node structure initialization. 1410 1411config RCU_TORTURE_TEST_SLOW_CLEANUP 1412 bool "Slow down RCU grace-period cleanup to expose races" 1413 depends on RCU_TORTURE_TEST 1414 help 1415 This option delays grace-period cleanup for a few jiffies 1416 between cleaning up each pair of consecutive rcu_node 1417 structures. This helps to expose races involving grace-period 1418 cleanup, in other words, it makes your kernel less stable. 1419 It can also greatly increase grace-period latency, especially 1420 on systems with large numbers of CPUs. This is useful when 1421 torture-testing RCU, but in almost no other circumstance. 1422 1423 Say Y here if you want your system to crash and hang more often. 1424 Say N if you want a sane system. 1425 1426config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY 1427 int "How much to slow down RCU grace-period cleanup" 1428 range 0 5 1429 default 3 1430 depends on RCU_TORTURE_TEST_SLOW_CLEANUP 1431 help 1432 This option specifies the number of jiffies to wait between 1433 each rcu_node structure cleanup operation. 1434 1435config RCU_CPU_STALL_TIMEOUT 1436 int "RCU CPU stall timeout in seconds" 1437 depends on RCU_STALL_COMMON 1438 range 3 300 1439 default 21 1440 help 1441 If a given RCU grace period extends more than the specified 1442 number of seconds, a CPU stall warning is printed. If the 1443 RCU grace period persists, additional CPU stall warnings are 1444 printed at more widely spaced intervals. 1445 1446config RCU_TRACE 1447 bool "Enable tracing for RCU" 1448 depends on DEBUG_KERNEL 1449 select TRACE_CLOCK 1450 help 1451 This option provides tracing in RCU which presents stats 1452 in debugfs for debugging RCU implementation. 1453 1454 Say Y here if you want to enable RCU tracing 1455 Say N if you are unsure. 1456 1457config RCU_EQS_DEBUG 1458 bool "Provide debugging asserts for adding NO_HZ support to an arch" 1459 depends on DEBUG_KERNEL 1460 help 1461 This option provides consistency checks in RCU's handling of 1462 NO_HZ. These checks have proven quite helpful in detecting 1463 bugs in arch-specific NO_HZ code. 1464 1465 Say N here if you need ultimate kernel/user switch latencies 1466 Say Y if you are unsure 1467 1468endmenu # "RCU Debugging" 1469 1470config DEBUG_WQ_FORCE_RR_CPU 1471 bool "Force round-robin CPU selection for unbound work items" 1472 depends on DEBUG_KERNEL 1473 default n 1474 help 1475 Workqueue used to implicitly guarantee that work items queued 1476 without explicit CPU specified are put on the local CPU. This 1477 guarantee is no longer true and while local CPU is still 1478 preferred work items may be put on foreign CPUs. Kernel 1479 parameter "workqueue.debug_force_rr_cpu" is added to force 1480 round-robin CPU selection to flush out usages which depend on the 1481 now broken guarantee. This config option enables the debug 1482 feature by default. When enabled, memory and cache locality will 1483 be impacted. 1484 1485config DEBUG_BLOCK_EXT_DEVT 1486 bool "Force extended block device numbers and spread them" 1487 depends on DEBUG_KERNEL 1488 depends on BLOCK 1489 default n 1490 help 1491 BIG FAT WARNING: ENABLING THIS OPTION MIGHT BREAK BOOTING ON 1492 SOME DISTRIBUTIONS. DO NOT ENABLE THIS UNLESS YOU KNOW WHAT 1493 YOU ARE DOING. Distros, please enable this and fix whatever 1494 is broken. 1495 1496 Conventionally, block device numbers are allocated from 1497 predetermined contiguous area. However, extended block area 1498 may introduce non-contiguous block device numbers. This 1499 option forces most block device numbers to be allocated from 1500 the extended space and spreads them to discover kernel or 1501 userland code paths which assume predetermined contiguous 1502 device number allocation. 1503 1504 Note that turning on this debug option shuffles all the 1505 device numbers for all IDE and SCSI devices including libata 1506 ones, so root partition specified using device number 1507 directly (via rdev or root=MAJ:MIN) won't work anymore. 1508 Textual device names (root=/dev/sdXn) will continue to work. 1509 1510 Say N if you are unsure. 1511 1512config CPU_HOTPLUG_STATE_CONTROL 1513 bool "Enable CPU hotplug state control" 1514 depends on DEBUG_KERNEL 1515 depends on HOTPLUG_CPU 1516 default n 1517 help 1518 Allows to write steps between "offline" and "online" to the CPUs 1519 sysfs target file so states can be stepped granular. This is a debug 1520 option for now as the hotplug machinery cannot be stopped and 1521 restarted at arbitrary points yet. 1522 1523 Say N if your are unsure. 1524 1525config NOTIFIER_ERROR_INJECTION 1526 tristate "Notifier error injection" 1527 depends on DEBUG_KERNEL 1528 select DEBUG_FS 1529 help 1530 This option provides the ability to inject artificial errors to 1531 specified notifier chain callbacks. It is useful to test the error 1532 handling of notifier call chain failures. 1533 1534 Say N if unsure. 1535 1536config CPU_NOTIFIER_ERROR_INJECT 1537 tristate "CPU notifier error injection module" 1538 depends on HOTPLUG_CPU && NOTIFIER_ERROR_INJECTION 1539 help 1540 This option provides a kernel module that can be used to test 1541 the error handling of the cpu notifiers by injecting artificial 1542 errors to CPU notifier chain callbacks. It is controlled through 1543 debugfs interface under /sys/kernel/debug/notifier-error-inject/cpu 1544 1545 If the notifier call chain should be failed with some events 1546 notified, write the error code to "actions/<notifier event>/error". 1547 1548 Example: Inject CPU offline error (-1 == -EPERM) 1549 1550 # cd /sys/kernel/debug/notifier-error-inject/cpu 1551 # echo -1 > actions/CPU_DOWN_PREPARE/error 1552 # echo 0 > /sys/devices/system/cpu/cpu1/online 1553 bash: echo: write error: Operation not permitted 1554 1555 To compile this code as a module, choose M here: the module will 1556 be called cpu-notifier-error-inject. 1557 1558 If unsure, say N. 1559 1560config PM_NOTIFIER_ERROR_INJECT 1561 tristate "PM notifier error injection module" 1562 depends on PM && NOTIFIER_ERROR_INJECTION 1563 default m if PM_DEBUG 1564 help 1565 This option provides the ability to inject artificial errors to 1566 PM notifier chain callbacks. It is controlled through debugfs 1567 interface /sys/kernel/debug/notifier-error-inject/pm 1568 1569 If the notifier call chain should be failed with some events 1570 notified, write the error code to "actions/<notifier event>/error". 1571 1572 Example: Inject PM suspend error (-12 = -ENOMEM) 1573 1574 # cd /sys/kernel/debug/notifier-error-inject/pm/ 1575 # echo -12 > actions/PM_SUSPEND_PREPARE/error 1576 # echo mem > /sys/power/state 1577 bash: echo: write error: Cannot allocate memory 1578 1579 To compile this code as a module, choose M here: the module will 1580 be called pm-notifier-error-inject. 1581 1582 If unsure, say N. 1583 1584config OF_RECONFIG_NOTIFIER_ERROR_INJECT 1585 tristate "OF reconfig notifier error injection module" 1586 depends on OF_DYNAMIC && NOTIFIER_ERROR_INJECTION 1587 help 1588 This option provides the ability to inject artificial errors to 1589 OF reconfig notifier chain callbacks. It is controlled 1590 through debugfs interface under 1591 /sys/kernel/debug/notifier-error-inject/OF-reconfig/ 1592 1593 If the notifier call chain should be failed with some events 1594 notified, write the error code to "actions/<notifier event>/error". 1595 1596 To compile this code as a module, choose M here: the module will 1597 be called of-reconfig-notifier-error-inject. 1598 1599 If unsure, say N. 1600 1601config NETDEV_NOTIFIER_ERROR_INJECT 1602 tristate "Netdev notifier error injection module" 1603 depends on NET && NOTIFIER_ERROR_INJECTION 1604 help 1605 This option provides the ability to inject artificial errors to 1606 netdevice notifier chain callbacks. It is controlled through debugfs 1607 interface /sys/kernel/debug/notifier-error-inject/netdev 1608 1609 If the notifier call chain should be failed with some events 1610 notified, write the error code to "actions/<notifier event>/error". 1611 1612 Example: Inject netdevice mtu change error (-22 = -EINVAL) 1613 1614 # cd /sys/kernel/debug/notifier-error-inject/netdev 1615 # echo -22 > actions/NETDEV_CHANGEMTU/error 1616 # ip link set eth0 mtu 1024 1617 RTNETLINK answers: Invalid argument 1618 1619 To compile this code as a module, choose M here: the module will 1620 be called netdev-notifier-error-inject. 1621 1622 If unsure, say N. 1623 1624config FAULT_INJECTION 1625 bool "Fault-injection framework" 1626 depends on DEBUG_KERNEL 1627 help 1628 Provide fault-injection framework. 1629 For more details, see Documentation/fault-injection/. 1630 1631config FAILSLAB 1632 bool "Fault-injection capability for kmalloc" 1633 depends on FAULT_INJECTION 1634 depends on SLAB || SLUB 1635 help 1636 Provide fault-injection capability for kmalloc. 1637 1638config FAIL_PAGE_ALLOC 1639 bool "Fault-injection capabilitiy for alloc_pages()" 1640 depends on FAULT_INJECTION 1641 help 1642 Provide fault-injection capability for alloc_pages(). 1643 1644config FAIL_MAKE_REQUEST 1645 bool "Fault-injection capability for disk IO" 1646 depends on FAULT_INJECTION && BLOCK 1647 help 1648 Provide fault-injection capability for disk IO. 1649 1650config FAIL_IO_TIMEOUT 1651 bool "Fault-injection capability for faking disk interrupts" 1652 depends on FAULT_INJECTION && BLOCK 1653 help 1654 Provide fault-injection capability on end IO handling. This 1655 will make the block layer "forget" an interrupt as configured, 1656 thus exercising the error handling. 1657 1658 Only works with drivers that use the generic timeout handling, 1659 for others it wont do anything. 1660 1661config FAIL_MMC_REQUEST 1662 bool "Fault-injection capability for MMC IO" 1663 depends on FAULT_INJECTION_DEBUG_FS && MMC 1664 help 1665 Provide fault-injection capability for MMC IO. 1666 This will make the mmc core return data errors. This is 1667 useful to test the error handling in the mmc block device 1668 and to test how the mmc host driver handles retries from 1669 the block device. 1670 1671config FAIL_FUTEX 1672 bool "Fault-injection capability for futexes" 1673 select DEBUG_FS 1674 depends on FAULT_INJECTION && FUTEX 1675 help 1676 Provide fault-injection capability for futexes. 1677 1678config FAULT_INJECTION_DEBUG_FS 1679 bool "Debugfs entries for fault-injection capabilities" 1680 depends on FAULT_INJECTION && SYSFS && DEBUG_FS 1681 help 1682 Enable configuration of fault-injection capabilities via debugfs. 1683 1684config FAULT_INJECTION_STACKTRACE_FILTER 1685 bool "stacktrace filter for fault-injection capabilities" 1686 depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT 1687 depends on !X86_64 1688 select STACKTRACE 1689 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC && !SCORE 1690 help 1691 Provide stacktrace filter for fault-injection capabilities 1692 1693config LATENCYTOP 1694 bool "Latency measuring infrastructure" 1695 depends on DEBUG_KERNEL 1696 depends on STACKTRACE_SUPPORT 1697 depends on PROC_FS 1698 select FRAME_POINTER if !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM_UNWIND && !ARC 1699 select KALLSYMS 1700 select KALLSYMS_ALL 1701 select STACKTRACE 1702 select SCHEDSTATS 1703 select SCHED_DEBUG 1704 help 1705 Enable this option if you want to use the LatencyTOP tool 1706 to find out which userspace is blocking on what kernel operations. 1707 1708config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1709 bool 1710 1711config DEBUG_STRICT_USER_COPY_CHECKS 1712 bool "Strict user copy size checks" 1713 depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS 1714 depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING 1715 help 1716 Enabling this option turns a certain set of sanity checks for user 1717 copy operations into compile time failures. 1718 1719 The copy_from_user() etc checks are there to help test if there 1720 are sufficient security checks on the length argument of 1721 the copy operation, by having gcc prove that the argument is 1722 within bounds. 1723 1724 If unsure, say N. 1725 1726source kernel/trace/Kconfig 1727 1728menu "Runtime Testing" 1729 1730config LKDTM 1731 tristate "Linux Kernel Dump Test Tool Module" 1732 depends on DEBUG_FS 1733 depends on BLOCK 1734 default n 1735 help 1736 This module enables testing of the different dumping mechanisms by 1737 inducing system failures at predefined crash points. 1738 If you don't need it: say N 1739 Choose M here to compile this code as a module. The module will be 1740 called lkdtm. 1741 1742 Documentation on how to use the module can be found in 1743 Documentation/fault-injection/provoke-crashes.txt 1744 1745config TEST_LIST_SORT 1746 bool "Linked list sorting test" 1747 depends on DEBUG_KERNEL 1748 help 1749 Enable this to turn on 'list_sort()' function test. This test is 1750 executed only once during system boot, so affects only boot time. 1751 1752 If unsure, say N. 1753 1754config KPROBES_SANITY_TEST 1755 bool "Kprobes sanity tests" 1756 depends on DEBUG_KERNEL 1757 depends on KPROBES 1758 default n 1759 help 1760 This option provides for testing basic kprobes functionality on 1761 boot. A sample kprobe, jprobe and kretprobe are inserted and 1762 verified for functionality. 1763 1764 Say N if you are unsure. 1765 1766config BACKTRACE_SELF_TEST 1767 tristate "Self test for the backtrace code" 1768 depends on DEBUG_KERNEL 1769 default n 1770 help 1771 This option provides a kernel module that can be used to test 1772 the kernel stack backtrace code. This option is not useful 1773 for distributions or general kernels, but only for kernel 1774 developers working on architecture code. 1775 1776 Note that if you want to also test saved backtraces, you will 1777 have to enable STACKTRACE as well. 1778 1779 Say N if you are unsure. 1780 1781config RBTREE_TEST 1782 tristate "Red-Black tree test" 1783 depends on DEBUG_KERNEL 1784 help 1785 A benchmark measuring the performance of the rbtree library. 1786 Also includes rbtree invariant checks. 1787 1788config INTERVAL_TREE_TEST 1789 tristate "Interval tree test" 1790 depends on m && DEBUG_KERNEL 1791 select INTERVAL_TREE 1792 help 1793 A benchmark measuring the performance of the interval tree library 1794 1795config PERCPU_TEST 1796 tristate "Per cpu operations test" 1797 depends on m && DEBUG_KERNEL 1798 help 1799 Enable this option to build test module which validates per-cpu 1800 operations. 1801 1802 If unsure, say N. 1803 1804config ATOMIC64_SELFTEST 1805 bool "Perform an atomic64_t self-test at boot" 1806 help 1807 Enable this option to test the atomic64_t functions at boot. 1808 1809 If unsure, say N. 1810 1811config ASYNC_RAID6_TEST 1812 tristate "Self test for hardware accelerated raid6 recovery" 1813 depends on ASYNC_RAID6_RECOV 1814 select ASYNC_MEMCPY 1815 ---help--- 1816 This is a one-shot self test that permutes through the 1817 recovery of all the possible two disk failure scenarios for a 1818 N-disk array. Recovery is performed with the asynchronous 1819 raid6 recovery routines, and will optionally use an offload 1820 engine if one is available. 1821 1822 If unsure, say N. 1823 1824config TEST_HEXDUMP 1825 tristate "Test functions located in the hexdump module at runtime" 1826 1827config TEST_STRING_HELPERS 1828 tristate "Test functions located in the string_helpers module at runtime" 1829 1830config TEST_KSTRTOX 1831 tristate "Test kstrto*() family of functions at runtime" 1832 1833config TEST_PRINTF 1834 tristate "Test printf() family of functions at runtime" 1835 1836config TEST_BITMAP 1837 tristate "Test bitmap_*() family of functions at runtime" 1838 default n 1839 help 1840 Enable this option to test the bitmap functions at boot. 1841 1842 If unsure, say N. 1843 1844config TEST_UUID 1845 tristate "Test functions located in the uuid module at runtime" 1846 1847config TEST_RHASHTABLE 1848 tristate "Perform selftest on resizable hash table" 1849 default n 1850 help 1851 Enable this option to test the rhashtable functions at boot. 1852 1853 If unsure, say N. 1854 1855config TEST_HASH 1856 tristate "Perform selftest on hash functions" 1857 default n 1858 help 1859 Enable this option to test the kernel's integer (<linux/hash,h>) 1860 and string (<linux/stringhash.h>) hash functions on boot 1861 (or module load). 1862 1863 This is intended to help people writing architecture-specific 1864 optimized versions. If unsure, say N. 1865 1866endmenu # runtime tests 1867 1868config PROVIDE_OHCI1394_DMA_INIT 1869 bool "Remote debugging over FireWire early on boot" 1870 depends on PCI && X86 1871 help 1872 If you want to debug problems which hang or crash the kernel early 1873 on boot and the crashing machine has a FireWire port, you can use 1874 this feature to remotely access the memory of the crashed machine 1875 over FireWire. This employs remote DMA as part of the OHCI1394 1876 specification which is now the standard for FireWire controllers. 1877 1878 With remote DMA, you can monitor the printk buffer remotely using 1879 firescope and access all memory below 4GB using fireproxy from gdb. 1880 Even controlling a kernel debugger is possible using remote DMA. 1881 1882 Usage: 1883 1884 If ohci1394_dma=early is used as boot parameter, it will initialize 1885 all OHCI1394 controllers which are found in the PCI config space. 1886 1887 As all changes to the FireWire bus such as enabling and disabling 1888 devices cause a bus reset and thereby disable remote DMA for all 1889 devices, be sure to have the cable plugged and FireWire enabled on 1890 the debugging host before booting the debug target for debugging. 1891 1892 This code (~1k) is freed after boot. By then, the firewire stack 1893 in charge of the OHCI-1394 controllers should be used instead. 1894 1895 See Documentation/debugging-via-ohci1394.txt for more information. 1896 1897config BUILD_DOCSRC 1898 bool "Build targets in Documentation/ tree" 1899 depends on HEADERS_CHECK 1900 help 1901 This option attempts to build objects from the source files in the 1902 kernel Documentation/ tree. 1903 1904 Say N if you are unsure. 1905 1906config DMA_API_DEBUG 1907 bool "Enable debugging of DMA-API usage" 1908 depends on HAVE_DMA_API_DEBUG 1909 help 1910 Enable this option to debug the use of the DMA API by device drivers. 1911 With this option you will be able to detect common bugs in device 1912 drivers like double-freeing of DMA mappings or freeing mappings that 1913 were never allocated. 1914 1915 This also attempts to catch cases where a page owned by DMA is 1916 accessed by the cpu in a way that could cause data corruption. For 1917 example, this enables cow_user_page() to check that the source page is 1918 not undergoing DMA. 1919 1920 This option causes a performance degradation. Use only if you want to 1921 debug device drivers and dma interactions. 1922 1923 If unsure, say N. 1924 1925config TEST_LKM 1926 tristate "Test module loading with 'hello world' module" 1927 default n 1928 depends on m 1929 help 1930 This builds the "test_module" module that emits "Hello, world" 1931 on printk when loaded. It is designed to be used for basic 1932 evaluation of the module loading subsystem (for example when 1933 validating module verification). It lacks any extra dependencies, 1934 and will not normally be loaded by the system unless explicitly 1935 requested by name. 1936 1937 If unsure, say N. 1938 1939config TEST_USER_COPY 1940 tristate "Test user/kernel boundary protections" 1941 default n 1942 depends on m 1943 help 1944 This builds the "test_user_copy" module that runs sanity checks 1945 on the copy_to/from_user infrastructure, making sure basic 1946 user/kernel boundary testing is working. If it fails to load, 1947 a regression has been detected in the user/kernel memory boundary 1948 protections. 1949 1950 If unsure, say N. 1951 1952config TEST_BPF 1953 tristate "Test BPF filter functionality" 1954 default n 1955 depends on m && NET 1956 help 1957 This builds the "test_bpf" module that runs various test vectors 1958 against the BPF interpreter or BPF JIT compiler depending on the 1959 current setting. This is in particular useful for BPF JIT compiler 1960 development, but also to run regression tests against changes in 1961 the interpreter code. It also enables test stubs for eBPF maps and 1962 verifier used by user space verifier testsuite. 1963 1964 If unsure, say N. 1965 1966config TEST_FIRMWARE 1967 tristate "Test firmware loading via userspace interface" 1968 default n 1969 depends on FW_LOADER 1970 help 1971 This builds the "test_firmware" module that creates a userspace 1972 interface for testing firmware loading. This can be used to 1973 control the triggering of firmware loading without needing an 1974 actual firmware-using device. The contents can be rechecked by 1975 userspace. 1976 1977 If unsure, say N. 1978 1979config TEST_UDELAY 1980 tristate "udelay test driver" 1981 default n 1982 help 1983 This builds the "udelay_test" module that helps to make sure 1984 that udelay() is working properly. 1985 1986 If unsure, say N. 1987 1988config MEMTEST 1989 bool "Memtest" 1990 depends on HAVE_MEMBLOCK 1991 ---help--- 1992 This option adds a kernel parameter 'memtest', which allows memtest 1993 to be set. 1994 memtest=0, mean disabled; -- default 1995 memtest=1, mean do 1 test pattern; 1996 ... 1997 memtest=17, mean do 17 test patterns. 1998 If you are unsure how to answer this question, answer N. 1999 2000config TEST_STATIC_KEYS 2001 tristate "Test static keys" 2002 default n 2003 depends on m 2004 help 2005 Test the static key interfaces. 2006 2007 If unsure, say N. 2008 2009source "samples/Kconfig" 2010 2011source "lib/Kconfig.kgdb" 2012 2013source "lib/Kconfig.ubsan" 2014 2015config ARCH_HAS_DEVMEM_IS_ALLOWED 2016 bool 2017 2018config STRICT_DEVMEM 2019 bool "Filter access to /dev/mem" 2020 depends on MMU 2021 depends on ARCH_HAS_DEVMEM_IS_ALLOWED 2022 default y if TILE || PPC 2023 ---help--- 2024 If this option is disabled, you allow userspace (root) access to all 2025 of memory, including kernel and userspace memory. Accidental 2026 access to this is obviously disastrous, but specific access can 2027 be used by people debugging the kernel. Note that with PAT support 2028 enabled, even in this case there are restrictions on /dev/mem 2029 use due to the cache aliasing requirements. 2030 2031 If this option is switched on, and IO_STRICT_DEVMEM=n, the /dev/mem 2032 file only allows userspace access to PCI space and the BIOS code and 2033 data regions. This is sufficient for dosemu and X and all common 2034 users of /dev/mem. 2035 2036 If in doubt, say Y. 2037 2038config IO_STRICT_DEVMEM 2039 bool "Filter I/O access to /dev/mem" 2040 depends on STRICT_DEVMEM 2041 ---help--- 2042 If this option is disabled, you allow userspace (root) access to all 2043 io-memory regardless of whether a driver is actively using that 2044 range. Accidental access to this is obviously disastrous, but 2045 specific access can be used by people debugging kernel drivers. 2046 2047 If this option is switched on, the /dev/mem file only allows 2048 userspace access to *idle* io-memory ranges (see /proc/iomem) This 2049 may break traditional users of /dev/mem (dosemu, legacy X, etc...) 2050 if the driver using a given range cannot be disabled. 2051 2052 If in doubt, say Y. 2053